Japan produced another stunning Rugby World Cup upset as Ireland were sensationally beaten 19-12 in a classic in Shizuoka.
The Brave Blossoms shocked the world with their victory over South Africa in England four years ago and, playing as hosts this time around, they were at it again on Saturday.
Ireland, who started the tournament as the world's top-ranked side, looked to be cruising when Jack Carty excelled in teeing up tries for Garry Ringrose and Rob Kearney.
But Yu Tamura's boot brought Japan back into contention before the break and a gutsy display in the second period was finally rewarded with Kenki Fukuoka's decisive score.
Joe Schmidt's men predictably came again but could find no way through a disciplined home outfit who are now on course to top Pool A and progress to the quarter-finals.
The final whistle sparked scenes of jubilation as Japan's players and fans celebrated a memorable victory on home soil, secured amid a tremendous atmosphere.
Ireland have never been past the last eight and, while they should still advance to that stage, two-time defending champions New Zealand would be their likely opponents if they finish second in the pool.
After an early Japan flurry, the Irish pressure built and Carty expertly picked out Ringrose with a crossfield kick for the opening try in the right corner.
Tamura landed a penalty in response, having missed an earlier effort, yet Ireland were now rampant and Carty knocked his own kick down for Kearney to lunge just inside the line for try number two.
However, the hosts rallied when many might have expected them to crumble and a pair of Tamura penalties heading into the break reduced the deficit to 12-9.
Ireland still could not shake off their dogged opponents, who earned another penalty for Tamura from range, only for his boot to let them down this time.
The Brave Blossoms were not to be denied when they next came forward, this time driving Ireland back towards their own try line and finally finding Fukuoka in space on the left for a breakthrough try.
Carty thrills briefly
Playing in Johnny Sexton's absence, Carty initially took his chance. He appeared to have identified a route through Japan and his early quick penalty almost got Keith Earls over in the corner. Carty repeated the trick for Ringrose and was rewarded, then played a key role in Kearney's score. But his control of the contest slipped as Japan roared forward.
Brave by name...
Japan made awful early errors against Russia that saw them battling against an upset. This time, playing as the underdogs, the Brave Blossoms were much improved from the first whistle but soon found themselves two tries down. Rather than shirk the challenge, the hosts offered a magnificent response and dictated the play for half an hour as Ireland wilted.
Japan face Samoa next and then Scotland but will be confident of beating both based on this performance. Ireland at least have a kind fixture in which to recover, facing minnows Russia.